I don't normally put lots of weight in the bed but last week I picked up about 2000lbs of gravel. Springs looked great, could have put twice that weight in before I hit the bumpers. As soon as I put her in drive and accelerated gently the 4x4 shifted started swinging wildly back and fourth. When I pulled out onto the road the trans was shaking so bad I thought I had really screwed up, but I found if I kept my rpms nice and high shifting manually I could smooth it enough to get the 1.8 miles home. Emptied the stone, test drive, WOT, everything seems fine.

I suspect the tight Goerends converter is to blame but wouldn't it do the same action pulling a trailer the same weight? I do that with no issues at all...

Can anybody point a finger at something else?

Thanks

 

Maybe when the suspension squatted under load it made a bad drive line angle.

 

X2

 

Ok so next time ill just make it 3000 lbs

 

if 2 thousand pounds did it 3 will make it works check your transfer case mounts see if they are squashed down if they are that might set the drive line angle off enough when hauling loads because we used to haul 1 cuard of firewood in the truck two on a trailer and never had that problem.

 

I think you guys are right because I have pulled lots more weight on a trailer and she ran fine. I'll have to stick to one scoop at a time, lucky for me then the store is only 1.8 miles away.

 

The only part that doesn't make sense is that it did the shaking much harder under acceleration, coasting was smooth even when in gear

 

Go look at your transfer case mounts they are rubber like a body mount and should be tall n not squished down n bulged out.

These trucks can haul more weight then that there's gotta be a problem under there.

 

I've put 5k in my bed many times and never had a shudder. Things were squatted right to the bump stops (well, almost)
I'd be checking the driveline. maybe the driveshaft for a ujoint or something. Checking the tcase mounts might be a good idea. maybe check around for cracks too. Something could be cracked and under the weight could be making something flex funny.

Check your transfer case fliud level too. My truck did something kinda similar under load when my rear output seal was leaking. Turned out the transfer case was like 1.5 qts low or something.

 

Beat me to the universal joint suggestion.

 

Check the usual suspects, tranny/transfer case mount, u joints, fluids but I'm x4 on the load being the issue. I did the same with mine, the ride was so smooth but it did shake more.

 

If your trams/transfer case mounts are bad I highly recommend poly ones from Poly bushings